Adding a timer switch to a water heater (need electrical and contactor advice)
I'm going to wire a countdown wall switch to a contactor that is rated to handle the water heater. I know they sell direct water heater timers, but those are big and bulky. The are also set time of day timers. I want something that I can set that will turn off after a set time once the switch has turned on. I have found many wall switches that do exactly this, but they are not rated for such high currents. So, I will use a contactor to do the job.
The diagrams I have seen show the wall switch to be wired directly to the contactor. First question: Will the contactor pull only the power that is needed or do I need to add a resistor so that it will pull significantly less power?
In the same line of thought, would I save any power by using a contactor that has a coil rated much lower than line voltage and using a resistor for the wall switch to achieve it?
My water heater wired up to two 20 amp circuit breakers. Should I assume that 20 amps is the max resistive load for each heating element? If so, will this contactor suffice?
Thank you all.